This application claims the priority benefit of Taiwan application serial no. 88120773, filed Nov. 29, 1999.
1. Field of Invention
The present invention generally relates to a method of forming a spacer for liquid crystal display (LCD) devices, and more particularly to a method of forming a spacer for a multi-domain vertical alignment (MVA) liquid crystal display devices.
2. Description of Related Art
Some of LCD device qualities, such as response time, contrast, viewing angle, etc., are all related to the thickness of the liquid crystal layer. The more uniform the thickness of LCD layer, the better the LCD device quality is. Thus, the thickness of LCD layer must be controlled critically. The thickness of LCD layer is almost determined by the height of spacers. The precision for a super twisted nematic (STN) type LCD device is usually limited to within 0.05-0.1 millimeters (mm).
For a normal LCD device, spacers are interposed between two glass substrates to maintain a predetermined cell gap therebetween. The spacers are formed randomly in the liquid crystal layer between the two glass substrates. As one skilled in the art knows, there are usually three kinds of spacers, with different sizes, including plate-shaped spacers, bar-shaped spacers and grain-shaped spacers. The plate-shaped spacers were the earliest to be developed. The plate-shaped spacers are set on the periphery of the liquid crystal layer. In contrast, the other two types of spacers, bar-shaped spacers and grain-shaped spacers, are dispersed within the liquid crystal layer. Among three of them, the plate-shaped spacers result in the worst display quality. The disadvantage of the plate-shaped spacers is that the sealant for packaging the LCD device diff-uses easily into the liquid crystal layer and between the spacers. Thus, it is difficult to maintain a predetermined cell gap between the two glass substrates. The bar-shaped spacers are better than the plate-shaped spacers. However, the disadvantage of the bar-shaped spacers is that organic and mineral material impurities usually contaminate the spacers during spinning to fabricate them. These organic and mineral material impurities degrade the display quality of the liquid crystal layer, and seriously disturb the arrangement of the liquid crystal molecules. As for the grain-shaped spacers, they are the most common technique used in the application of LCD devices, because the grain-shaped spacers can overcome the above disadvantages. The method of manufacturing the grain-shaped spacers includes spraying plastic balls or silicon glass fibers.
FIG. 1 is a schematic, cross-sectional diagram showing a conventional LCD device having grain-shaped spacers. Two glass substrates 10a and 10b are provided, wherein the glass substrate 10a is an upper glass substrate and the glass substrate 10b is a lower glass substrate. A color filter 11 is formed on the surface of the upper glass substrate 10a facing the lower glass substrate 10b. The color filter 11 includes red (R), green (G) and blue (B) films. Next, a plurality of protrusions 12 are formed on the color filter 11 to get multi-domain regions in a single pixel. The liquid crystal molecules in every are pre-tilted with a specific orientations to improve the displays"" viewing angle. In addition, a pixel electrode 14 is formed on the surface of the lower glass substrate 10b facing the upper glass substrate 10a. A switching element 14a, for example a thin film transistor (TFT), is also formed on the surface of the lower glass substrate 10b facing the upper glass substrate 10a for enabling/disabling the corresponding pixel to receive data signals. A liquid crystal layer 16 is interposed between the upper glass substrate 10a and the lower glass substrate 10b. Spacers 18 are randomly distributed within the liquid crystal layer 16. The spacers 18 are interposed between the two glass substrates (10a, 10b) to maintain a predetermined cell gap between the two glass substrates (10a, 10b).
The disadvantage of the grain-shaped spacers 18 is that the spacers 18 distribute randomly within the liquid crystal layer 16, making impossible the precise control of the location of the spacers 18. With that, some qualities of the LCD device, such as open ratio, transmittance and arrangement of liquid crystal molecules, will be degraded. In worse case, some spacers 18 , such as spacer 18a, are situated below the protrusions 12 as shown in FIG. 1. That results in a pressure difference within the liquid crystal layer 16 and the thickness of the liquid crystal layer 16 will not be consistent. Accordingly, the spacers cannot maintain a uniform cell gap between the two glass substrates (10a, 10b).
Accordingly, the object of the present invention is to provide a method of forming a spacer for LCD devices for resolving the above conventional problems.
One object of the present invention is to provide a method of forming a spacer for LCD devices for controlling the location of spacers within a liquid crystal layer.
Another object of the present invention is to provide a method of forming a spacer for LCD devices to improve the uniformity of the thickness of the liquid crystal layer.
The present invention provides a method of forming a spacer for LCD devices comprises the following steps. A substrate is provided. A pre-spacer material and a protrusion material are also provided. The materials of the pre-spacer material include a cyanuric acid, a resin with urea, a benzoguanamine resin, or a glass fiber. The materials of the protrusion material include a photosensitive resin. Then, a mixed material is formed by mixing the pre-spacer material and the protrusion material with a predetermined ratio. Then, the mixed material is coated on the substrate. An exposure step and a development step are performed to pattern the mixed material for forming a protrusion-spacer structure on the substrate, wherein the pre-spacer material is situated only where the on the protrusion is formed. Accordingly, each protrusion-spacer structure has the same height. And it is easy to get uniform cell gap between the substrate.
There are many methods for forming the above mixed material. For example, the first method comprises the steps of: adding a melamine resin to a formaldehyde, the melamine resin reacting with the formaldehyde to form a solution of amino resin; adding a sulfuric acid (which acts as a hardening catalyst) to the amino resin solution; mixing the amino resin solution with the protrusion material; and churning and polymerizing the above materials. The second method of forming the mixed material comprises the steps of: adding a urea resin to formaldehyde to form a solution of amino resin; adding sulfuric acid to the amino resin solution (the sulfuric acid acts as a hardening catalyst); mixing the amino resin solution with the protrusion material; and churning and polymerizing the above materials. The third method of forming the mixed material comprises the steps of: adding a benzoguanamine resin to formaldehyde to form an intermediate; adding the intermediate to a solution consisting of polyethylene to form a galactoid solution; adding a hardening catalyst and mixing the galactoid solution with the protrusion material; and performing sequentially the steps of heating, disengaging, cleaning and drying to form a hardened resin. The fourth method of forming the mixed material comprises the steps of adding a small amount of melamine resin to a benzoguanamine resin, and mixing the resulting resin with the protrusion material to let all of the materials react with each other.
The other method of forming LCD devices with a spacer comprises providing a first substrate and a second substrate, with a color filter film formed on the first substrate facing the second substrate and a pixel electrode matrix formed on the second substrate facing the first substrate. A pre-spacer material and a protrusion material are provided. The materials of the pre-spacer material include a cyanuric acid, a resin with urea, or a benzoguanamine resin. The materials of the protrusion material include a photosensitive resin. A mixed material is formed by mixing the pre-spacer material and the protrusion material with a predetermined ratio. Then the mixed material is coated on the first substrate facing the second substrate. An exposure step and a development step are performed on the mixed material to pattern the mixed material to form a plurality of protrusion-spacer structures on the first substrate, wherein the spacer is situated only where the protrusion is formed. Accordingly, each protrusion-spacer structure has the same height. Then, the first substrate and the second substrate are sealed together. The cell gap between the first substrate and the second substrate is determined by the height of the protrusion-spacer structures. Therefore, it is easy to get uniform cell gap between the first substrate and the second substrate.
There are many methods for forming the above mixed material. For example, the first method comprises the steps of: adding a melamine resin to a formaldehyde, the melamine resin reacting with the formaldehyde to form a solution of amino resin; adding a sulfuric acid (which acts as a hardening catalyst) to the amino resin solution; mixing the amino resin solution with the protrusion material; and churning and polymerizing the above materials. The second method of forming the mixed material comprises the steps of: adding a urea resin to formaldehyde to form a solution of amino resin; adding sulfuric acid to the amino resin solution (the sulfuric acid acts as a hardening catalyst); mixing the amino resin solution with the protrusion material; and churning and polymerizing the above materials. The third method of forming the mixed material comprises the steps of: adding a benzoguanamine resin to formaldehyde to form an intermediate; adding the intermediate to a solution consisting of polyethylene to form a galactoid solution; adding a hardening catalyst and mixing the galactoid solution with the protrusion material; and performing sequentially the steps of heating, disengaging, cleaning and drying to form a hardened resin. The fourth method of forming the mixed material comprises the steps of adding a small amount of melamine resin to a benzoguanamine resin, and mixing the resulting resin with the protrusion material to let all of the materials react with each other.
Another method of forming a LCD device having spacers comprises providing a first substrate and a second substrate, with a color filter film formed on the first substrate facing the second substrate and a pixel electrode matrix formed on the second substrate facing the first substrate. A pre-spacer material and a black matrix material are provided. The materials of the pre-spacer material include a cyanuric acid, a resin with urea, or a benzoguanamine resin. The materials of the black matrix material include a photosensitive resin. A mixed material is formed by mixing the pre-spacer material and the black matrix material with a predetermined ratio. Then the mixed material is coated on the first substrate facing the second substrate. An exposure step and a development step are performed to pattern the mixed material to form a plurality of black-matrix-spacer structures , wherein the black matrix is formed on the first substrate and the spacer is situated on the first substrate only where the black matrix is formed. The first substrate and the second substrate are sealed together. The cell gap between the first substrate and the second substrate is controlled by the height of the protrusion-spacer structures. According to the present invention, it is easy to form the black-matrix-spacer structure with uniform height. Therefore, a LCD device with uniform cell gap is easily produced.
There are many methods for forming the mixed material. For example, the first method comprises the steps of: adding a melamine resin to a formaldehyde to form a solution of amino resin; adding a sulfuric acid (which acts as a hardening catalyst) to the amino resin solution; mixing the amino resin solution with the black matrix material; and churning and polymerizing the above materials. The second method of forming the mixed material comprises the steps of: adding a urea resin to formaldehyde to form a solution of amino resin; adding sulfuric acid (which acts as a hardening catalyst) to the amino resin solution; mixing the amino resin solution with the black matrix material; and churning and polymerizing the above materials. The third method of forming the mixed material comprises the steps of: adding a benzoguanamine resin to formaldehyde to form an intermediate; adding a churning solution consisting of polyethylene to the intermediate to form a galactoid solution; adding a hardening catalyst and mixing the galactoid solution with the black matrix material; and performing the steps of heating, disengaging, cleaning and drying to form a hardened resin. The fourth method of forming the mixed material comprises adding a small amount of melamine resin to a benzoguanamine resin, and mixing the resulting resin with the black matrix material to let all of the materials react with each other.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.